Abstract
This paper showed physiological fluxes (H+, O2, and Cd2+ fluxes) and the antioxidative defense system of PTNs. [Display omitted]
•Physiological fluxes of PTNs indicated the instaneous response to 2,4-DCP and Cd2+.•H+, O2, and Cd2+ fluxes of PTNs were measured by the NMT.•The antioxidative defense system of PTNs after exposed to Cd2+ was developed.
Immobilized Phanerochaete chrysosporium loaded with TiO2 nanoparticles (PTNs) are novel high-value bioremediation materials for adsorbing cadmium and for degrading 2,4-dichlorophenol (2,4-DCP). The real-time changes in H+ and O2 fluxes were measured using the noninvasive microtest technique (NMT). The H+ influx increased after the addition of 2,4-DCP, and shifted to efflux following the addition of Cd2+. The O2 flux decreased after the addition of both 2,4-DCP and Cd2+. A larger Cd2+ flux was immediately observed after exposure to 0.5mM Cd2+ (−351.25pmolcm−2s−1) than to 0.1mM Cd2+ (−107.47pmolcm−2s−1). The removal of Cd2+ by the PTNs increased more after treatment with the 0.5mM exposure solution (27.6mgg−1) than with the 0.1mM exposure solution (3.49mgg−1). The enzyme activities were analyzed to review the antioxidative defense system of PTNs in a solution containing various concentrations of Cd2+. The activities of the coenzyme nicotinamide adenine dinucleotide (NADH) oxidase as well as the enzyme catalase (CAT) plateaued at 6.5Ug−1 FW and 9.7Ug−1 FW, respectively, after exposure to 0.25mM Cd2+. The activity of superoxide dismutase (SOD) increased gradually in solutions containing 0.1–0.6mM Cd2+, and eventually reached a maximum (68.86Ug−1 FW). These results illustrate how the antioxidative defense system and the physiological fluxes of PTNs respond to the stress caused by toxic pollutants.